Stomatal closure

Bates, L.M. Hall, A.E. (1981). Stomatal closure with soil water depletion not associated with changes in bulk leaf water status. Oecologia, 50, 62-5. 

Downton, W.J.S., Loveys, B.R. Grant, W.J.R. (1988). Stomatal closure fully accounts for the inhibition of photosynthesis by abscisic acid. New Phytologist, 108, 263-6. 

McCree, K.J. Richardson, S.G. (1987). Stomatal closure vs. osmotic adjustment a comparison of stress responses. Crop Science, 27, 539-43. 

Within the plant. Excessive concentrations of some ions occur in the tissue overall, in the cytoplasm, or in the apoplast. Effects include metabolic inhibition, interference with protein synthesis, cellular dehydration, stomatal closure and early senescence of leaves. Since both cytoplasm and apoplast are small compartments, imbalance between compartments may amplify the effects of excess salt, resulting in toxicity despite apparently moderate overall tissue concentrations. 

Unfavorable temperatures, especially when suddenly imposed, have been shown to cause leakage of ions and metabolites from the root to the surrounding medium (188). In addition, sudden changes of temperature cause a lowering of conductivity to water of roots and inhibition of ion transport (188). This can indirectly affect the carbon economy of the whole plant by leading to more negative leaf water potentials, partial stomatal closure, and hence a slowing of net CO2 assimilation. 

The reported (14) mechanisms of action of allelochemlcals Include effects on root ultrastructure and subsequent Inhibition of Ion absorption and water uptake, effects on hormone-induced growth, alteration of membrane permeability, changes In lipid and organic acid metabolism, inhibition of protein synthesis and alteration of enzyme activity, and effects on stomatal opening and on photosynthesis. Reduced leaf water potential Is one result of treatment with ferulic and p-coumaric acids (15). Colton and Einhellig (16) found that aqueous extracts of velvetleaf (Abutllon theophrastl Medic.) Increased diffusive resistance In soybean fGlycine max. (L.) Merr.] leaves, probably as a result of stomatal closure. In addition, there was evidence of water stress and reduced quantities of chlorophyll In Inhibited plants. 

During drought stress, ABA regulates stomatal closure, whereas increased ethylene production has an inhibitory influence on ABA action. An inhibition of ethylene synthesis delays drought-associated chlorophyll loss, supporting the role of ethylene in drought-induced senescence. °°... 

Stomata are the principal entry sites for ozone and PAN into plant leaves, and stomatal closure effectively protects the plant from in-jury. Several studies suggest that oxidants may cause stomatal closure. ... 

Stomatal closure was associated with a genetic factor in onion wherein the stomata of sensitive plants did not close. The effect of ozone and PAN on stomatal opening depends on many interacting factors those representing water stress appear to be the most important. Dean related stomatal density to the difference in sensitivity between two tobacco cultivars. Evans and Ting found that maximal sensitivity of bean primary leaves was not associated with changes in stomatal number or leaf resistance. Ozone exposure caused a decrease in relative water content, but no change in resistance. Bean leaf sensitivity seemed more a function of internal activities. 

Physiologic Effects The physiologic effects of ozone depend on its entry into the internal leaf spaces through the stomata. If the plant is resistant to ozone even when stomata remain open, mechanisms of resistance other than stomatal closure must be operative. The physiologic effects measureable with the intact tissue include effects on respiration and photosynthesis. 

Genetic or other factors that induce stomatal closure will reduce plant sensitivity to oxidant pollutants. Generally, the sensitivity of plants at the time of exposure is controlled primarily by factors that affect the stomatal aperture. The internal resistance to gas flow may also influence leaf sensitivity. Factors that affect sensitivity during growth usually cause physiologic changes in the plant that tend to make it more resistant to the added stress of oxidant. Many of these stresses may alter membrane physiology and make the membranes either more or less sensitive to oxidant stress. 

Hill, A. C., and N. Littlefield. Ozone. Effect on apparent photo thesis, rate of transpiration, and stomatal closure In plants. Environ. Sci. Technol. 3 52-56, 1969. 

Plant sensitivity to ozone, PAN, and other oxidants is conditioned by many factors. Genetic diversity between species and between cultivars within a species is well documented. The mechanism of genetic resistance is known for only one onion cultivar and is related to the effect of ozone on stomatal closure. Variants within a natural species are well known for several pine species, including white, loblolly, and ponderosa. 

Although stomata in plants treated with HF and SO2 showed some tendency to close as a result of exposures which depressed apparent photosynthetic rates, these phytotoxicants inhibited CO2 uptake rates more by affecting biochemical processes within the leaves than by impeding gas transfer by inducing stomatal closure. 

Mulch A, Chamberlain CP (2007) Stable isotope paleoaltimetry in orogenic belts - the silicate record in surface and crustal geological archives. Rev Mineral Geochem 66 89-118 Nogues S, Allen DJ, Morison JIL, Baker NR (1998) Ultraviolet-B radiation effects on water relations, leaf development, and photosynthesis in draughted pea plants. Plant Physiol 117 173-181 Nogues S, Allen DJ, Morison JIL, Baker NR (1999) Characterization of stomatal closure caused by ultraviolet-B radiation. Plant Physiol 121 489-496... 

DPA did not cause stomatal closure In any of the species tested, while the effect of PA ranged from a response as rapid as that caused by ABA in Commelina, to a less rapid closure than after ABA treatment in Amaranthus, Hordeum, Xanthium, and Zea, to no response at all in Vicia (76). 

One further problem is the large overshoot in ABA production in wilted leaves. With applied ABA a doubling of the ABA content of the leaf is usually adequate for stomatal closure, while increases up to 40-fold have been reported in wilted leaves. However, extractions of whole leaves do not take into account the location of ABA within the leaf. Perhaps much of the hormone is sequestered in a compartment that has no access to the guard cells. Thus, it would be of much importance to determine the distribution of ABA at the tissue level as well as its intracellular location. Since ABA is a small water-soluble molecule, conventional fractionation techniques may not be suitable to determine its distribution in various organelles. A highly specific immunological method for detection of ABA has recently been developed (38, 39). It is conceivable that this technique could be further developed for determining the cellular localization of ABA as has already been done for the photoreceptor phytochrome (77, 78). 

The primary inhibitory effect of cadmium on photosynthesis of excised leaves was proposed to be metal-induced stomatal closure (Bazzaz et al., 1974 Lamoreaux and Chaney, 1978). In epidermal peels floating on a metal-containing solution, stomatal closure was reported (Bazzaz et al., 1974). Inhibition of transpiration by several metals, especially by cadmium, is well documented (Poschenrieder et al., 1989), but is not necessarily at the stomatal level. Metal-induced stomatal closure can indirectly be responsible for a decrease of photosynthetic C02 fixation indeed. However, several enzymes of the Calvin cycle are directly affected by metals. 

Much like the phenolic acids, early work with scopoletin showed it inhibited oxidation of IAA and thus could affect growth in this manner. Inhibition of several other enzymes by scopoletin and coumarin has been shown. Coumarin was reported to induce ethylene synthesis.47 Also, it is one of several phenolic compounds that antagonize abscisic acid-induced inhibition of growth and stomatal closure.52 Undoubtedly, these and possibly other interactions with hormones are part of the physiological action of the coumarins. 

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